Ventilation can either be done passively through openings or mechanically with fans. Roll up sides are an economical way of getting lots of air movement since no electricity is required. Roll up sides become even more effective when used on longer buildings. Roll up sidewalls are often used in combination with a small exhaust fan for early and late season ventilation when opening the sides is not practical.

If a structure is very exposed, it is best not to open more then 3’ in height due to potential of wind damage. If a structure is extremely sheltered, it is best to go even up to 6’ to create maximum opening. Roll up sidewalls are most effective when used in combination with peak end wall vents to create a “chimney effect” to draw warm air out of the building, especially when it is very calm. These vents are effective for air movement when outside temperature does not allow opening of the sides.

When a structure has a low profile, you will need to be careful during rainy periods due to moisture getting into the structure area. High profile structures (with straighter walls) usually work better with roll up sidewalls. When preventing a floor draft is an issue, the roll up mechanism can be raised and then the structure is lined with a skirt for the bottom 2’-3’. When using this method of ventilation, it should always be done on both sides. An effective use of this method includes opening the “downwind side totally and the opposite side on marginally.

We have been continuing to get many inquiries about solar powering the inflator fan for greenhouses and livestock buildings, which is used to put air between two layers of plastic roof cover. For the last year we have been experimenting with a solar collecting package to determine what is required, while we work to keep our interested customers updated along the way.

The first thing that must be emphasized, is that you MUST use a squirrel cage type of fan and not a propeller type. The propeller type can not continuously run against back pressure.

The output required will be determined by the size of the greenhouse or livestock building. Our regular 110 volt fan draws .25 amp and puts out 80 cfm. Some small buildings can use a smaller fan and some of the bigger ones require our double output fan which gives 130 cfm.

Our inflator fan works quite well going through an invertor. Any 12 or 24 volt fans which we have tried have been extremely noisy and therefore not feasible.

The biggest challenge which we encountered, is that the specific time the fan is needed the most for heat insulation, is also the time where there is the least capacity for generating power.

We used a single solar collector and a single battery and there was simply not a quick enough capacity for the battery to hold charge when we had several consecutive cloudy days in December/January

To add another solar collector to an already fairly expensive package, really becomes prohibitive and can deter from moving forward with it.

Based on this experience, we wanted to offer an alternative that balanced economy with feasibility. We have come up with a way where the extra roof plastic can be used on the inside of the structure.

This means that you would not need the inflator fan but still have the effect of double plastic with the air pocket for better heat efficiency. This system does require a bit of extra “fiddling” but the net cost will be a little less.

1. The structure is covered with a single layer of plastic just the same as you would if you were only doing a single layer.
2. Take the second piece of plastic inside the greenhouse and fold it double lengthwise.
3. This double plastic will be attached to the underside of the ridge using the same aluminum as you would use to fasten the plastic to the roll up pipe.
4. Next remove the purlins from the one side of the structure and after you have pushed over the plastic, reinstall the purlins under the plastic. You will be pushing the bolts through the plastic.
5. The plastic will be fastened with wirelock to the underside of the end hoops.

We have already had some customers try this out and are very happy with the result. Please call us with any questions or to discuss your specific application and situation where you might use this. We would be happy to help you with your project!